Lean Six Sigma Green Belt Certification Improve Phase and Solutions 2 — Questions and Answers
Question 1: In a Design of Experiments (DOE), what is the purpose of a 'center point'?
- To identify the optimal factor settings
- To detect curvature in the response surface (Correct answer)
- To reduce the number of experimental runs
- To randomize the order of experiments
Correct answer: To detect curvature in the response surface
Center points are added to a factorial design to detect nonlinear (curved) relationships between factors and the response.
Question 2: A project team wants to pilot a solution before full deployment. Which tool best structures the pilot plan?
- Fishbone diagram
- Control chart
- Pilot plan with PDCA cycle (Correct answer)
- Pareto chart
Correct answer: Pilot plan with PDCA cycle
A pilot plan using the PDCA (Plan-Do-Check-Act) cycle structures the test, measurement, and review of a solution before full rollout.
Question 3: What does 'mistake-proofing' (poka-yoke) primarily target in a process?
- Reducing cycle time
- Preventing defects by making errors impossible or immediately detectable (Correct answer)
- Increasing production speed
- Eliminating unnecessary process steps
Correct answer: Preventing defects by making errors impossible or immediately detectable
Poka-yoke devices are designed to prevent errors from occurring or to detect them immediately if they do occur.
Question 4: Which type of waste in Lean is represented by excess inventory beyond what is immediately needed?
- Motion
- Overproduction
- Waiting
- Inventory (Correct answer)
Correct answer: Inventory
Inventory waste refers to excess materials, WIP, or finished goods that occupy space and tie up capital without adding value.
Question 5: A team implements a solution and measures a 40% reduction in defects. What is the NEXT step in the Improve phase?
- Archive the project files
- Verify the improvement is statistically significant and sustainable (Correct answer)
- Begin a new DMAIC project
- Expand the solution to all sites immediately
Correct answer: Verify the improvement is statistically significant and sustainable
After measuring improvement, the team must verify statistical significance and sustainability before declaring success or expanding.
Question 6: In a 2^3 full factorial DOE, how many experimental runs are required (excluding replicates)?
- 4
- 6
- 8 (Correct answer)
- 16
Correct answer: 8
A 2^3 full factorial design with 3 factors each at 2 levels requires 2³ = 8 experimental runs.
Question 7: Which lean tool is used to visually balance workload across operators to match customer takt time?
- Spaghetti diagram
- Operator balance chart (Correct answer)
- Value stream map
- 5S audit sheet
Correct answer: Operator balance chart
An operator balance chart (also called a work balance chart) displays each operator's cycle time against takt time to identify imbalances.
Lean Six Sigma Green Belt Certification Improve Phase and Solutions 2
In a Design of Experiments (DOE), what is the purpose of a 'center point'?